Google's legal representatives will have to appear before a Spanish court in October to explain the company's collection of details of people's Wi-Fi networks and transmissions.

The Spanish Legal Advanced Communications and Computer Crime Association (Apedanica), an internet rights group, said on Monday that a Madrid court had ordered the appearance for 4 October. Google will have to give details of the instruments used to collect the data, the nature of the data itself and the number of customers affected.

"We are working with the relevant authorities in Spain to answer any questions they may have," a Google spokesperson told ZDNet UK on Wednesday.

Apedanica complained to the Spanish authorities about Google's network-sniffing in June, after the company's practice came to light in April. It was the German data protection czar who first complained that Google's Street View cars had been collecting details of people's media access control (MAC) addresses and service set identifiers (SSIDs) as they drove around, photographing buildings for Google Maps.

Google said the router information was collected in order to aid location-based services. However, it subsequently emerged that contrary to the company's initial statement on the matter, Google had also collected pieces of people's Wi-Fi transmissions, such as password and fragments of emails. Google blamed this on rogue code that had snuck into the Street View cars' systems.